The relationship between several observations of DNA repair activities in cells treated with radiations and selected chemical carcinogens, and the biological fate of treated cells will continue to be examined. The DNA repair activities which will be studied are: unscheduled DNA synthesis, gross rejoining kinetics of gamma-ray induced DNA strand breaks, rapid kinetics of a cyclical DNA incisional process in gamma-irradiated cells, G2-repair of UVL-irradiated cells, and post-rejoining DNA disassembly in gamma-irradiated cells. The role these processes play in cell death, cell inactivation, transformation and accelerated aging will be studied in several cell systems appropriate to each of these cellular endpoints.